Classes

• A class is a compound data structure.
• They have member functions as well as data members.
  • We choose which member functions to have, what their names are, what they do and when they are called.
  • Members determine the behaviour of objects of the class.
  • They are called to perform operations on an object.
• By default, access to class members is private.
  • Only objects of the class can access a private member.
• Class members can be made public.
  • A public member can be accessed by any code in the program.

Public and Private Members

• The public members provide the interface of the class.
  • AKA what it does.
• The private members provide the implementation of the class.
  • AKA how it does it.
• A struct is the same as a class, except all the members are public by default.

Member Function Implementation

• Member functions are implemented as global functions.
• When a member function is called on an object, the object is passed by address in a hidden argument.

  Test test;
  test.func(1,2.0, "three"); // Called as Test::func(&test,1,2.0,"three")

• The pointer to the object is available as this in the function.
• Dereferencing this gives access to members of the object.

  // in the body of Test::func()
  this->i = 1; // or just i = 1
  // "this" is equivalent to &test